在带有标记文本的 altair 中对条形图进行排序时出现问题

Question

chart_df= alt.Chart(df).mark_bar().encode(
    x = 'value',
    y = alt.Y('name', sort='-x'),
    color = 'variable'
)

为了将每个条形图的值添加为文本，我使用了以下代码，但我丢失了排序的条形图。

chart_df_text = chart_df.mark_text().encode(
    x = 'text_margin_from_bar:Q',
    text = 'human_readable_value:Q',
).transform_calculate(
    human_readable_value = expr.toString(expr.floor(datum.value/10**7)),
    text_margin_from_bar = datum.value + (datum.value/expr.abs(datum.value))*1000000000
    # i have negetive and positive numbers, so for have a space between number and bar, i do this
)

添加

y = alt.Y('name', sort='-x'),

到 chart_df_text 但我仍然有问题。我读了另一个有我问题的问题，说问题是 altair 的版本，但我在最后一个。

Answer 1

javascript 控制台中的警告告诉您为什么这不起作用：

[Warning] Dropping sort property {"field":"value","op":"sum"} as unioned domains only support boolean or op "count", "min", and "max".
[Warning] Domains that should be unioned has conflicting sort properties. Sort will be set to true.

您可以通过在排序中使用受支持的 op 来解决此问题。例如：

import pandas as pd
import altair as alt
from altair import expr, datum

df = pd.DataFrame({
    'value': [-3E9, -4E9, 6E9, 1E10, -8E9],
    'name': ['Bob', 'Sue', 'Tim', 'Ann', 'Bill'],
    'variable': range(5)
})

chart_df= alt.Chart(df).mark_bar().encode(
    x = 'value',
    y = alt.Y('name', sort=alt.EncodingSortField('value', op='min', order='descending')),
    color = 'variable'
)

chart_df_text = chart_df.mark_text().encode(
    x = 'text_margin_from_bar:Q',
    text = 'human_readable_value:Q',
).transform_calculate(
    human_readable_value = expr.toString(expr.floor(datum.value/10**7)),
    text_margin_from_bar = datum.value + (datum.value/expr.abs(datum.value))*1000000000
)

chart_df + chart_df_text

在带有标记文本的 altair 中对条形图进行排序时出现问题

problem in sorting bar chart in altair that layered with a mark text

python

altair